There are two types of lube: one is straight 80W90 either synthetic or not- synthetic. The second is the same but with a portion of limited-slip additive, sometimes called "Positraction Additive". This material allows a bit of slip in your limited-slip clutches and prevents jerking from stick/slip/stick in tight turns. Its especially noticeable in rain/snow or on other low-traction surfaces.
If your car has badly worn limited slip clutches (3 per side), your won't notice the jerking. So I prefer lube with the additive; it can't hurt and may help low speed handling. Or, you can add anti-slip yourself to plain lube. GM EOS or other; not expensive & doesn't seem to wear out. Note that the Pantera is 50+ yrs old and some mistreated cars still have the original lube. ZF says to change it regularly. As for a long travel slave, the vendors are your best bet. Some are stainless steel.